Prior art in scotch yoke devices is limited to devices in which the slot or raceway of the yoke is perpendicular to the reciprocating member. A perpendicular slot produces an erratic stroke of the reciprocating member. Maximum power and minimum velocity of the reciprocating member occurs at the beginning and end of the stroke, and minimum power and maximum velocity occurs at midstroke.
J. W. Hall's Mechanism For Converting Rotary To Reciprocating Movement, U.S. Pat. No. 1,385,002, 7/19/21, features a cam pin mounted between two revolving disks and alternately engaging cam tracks in the disks.